This section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the present invention. The following discussion is intended to provide information to facilitate a better understanding of the present invention. Accordingly, it should be understood that statements in the following discussion are to be read in this light, and not as admissions of prior art.
In most telephone networks, there are examples of telephone numbers that are configured to route calls to that number to different destinations based on where the caller is placing the call from. For example, the common 211 community service code (which connects people with important community services and volunteer opportunities), is intended to route the caller to services that are relevant to the location they are calling from in other cases, there are numbers that are only valid when dialed in limited, areas. For example, dialing *55 from a cell phone in Oklahoma will deliver the caller to highway emergency assistance, whereas in Texas *377 must be used. These are examples of Geo-Local numbers: Telephone numbers that are only valid, or perhaps have different target destinations, when called from specific geographic areas. There are many other examples of such geo-local services (411, *pizza, etc.).
In the IP Multimedia System (IMS), the network architecture is such that when a subscriber roams to another network, network elements belonging to the visited network handle some portions of the call control, while other network elements, located in the subscriber's home network, provide other portions of the call control. The architecture has been defined such that the network elements that are to analyze the dialed digits and provide routing functions are in the user's home network. This is largely done for consistency, so that services and their interactions, such as call forwarding, call transfer, call waiting, etc. work consistently regardless of where the user is roaming.
As described, in the IP Multimedia System (IMS), services and routing decisions are handled in the user's home network. However, when a user roams to another geographic area, their home network will likely not understand how to properly route calls made to geo-local numbers from another location. In the example provided above, the home network would need to have a database that mapped all of the Oklahoma highway assistance centers, their full local routing numbers, and all of the geographic boundaries defined for each of them. It would need the same database for Texas, California, Nevada, etc. This gets even more difficult if you consider a roamer visiting Oklahoma whose home network is in Sweden.
There are two problems that need to be addressed. The first is obviously scaling. It becomes quickly unmanageable if each network provider that supports subscribers roaming to foreign ‘partner’ networks needs to maintain a database of the geo-local numbers and the resolution/translation rules for each partner. Secondly, there may be problems related to information integrity and security. Partner networks may not wish to provide their mutable access numbers for each of these services to other network providers.